ABSTRACT: This work introduces WUDESIM, an open-source C/C++ toolkit for modeling water quality in the dead- end branches of drinking water distribution networks. WUDESIM is linked to the programmers’ toolkit of EPANET, a widely-used public-domain water network analysis model. In place of the advection-based water quality module in EPANET, WUDESIM allows the users to simulate water quality in the pipes of dead-end branches with dispersion as a constituent transport mechanism. In addition, WUDESIM corrects for the simulation errors that arise from the spatial aggregation of water demands due to network skeletonization, and enables the users to use stochastically-generated water demands at fine time-scales. The software comprises two components: a Windows® executable file and a C/C++ dynamic link library (DLL) toolkit. Examples of how the users can employ the different toolkit functions to run water quality analysis and obtain simulation results are provided. WUDESIM is available as a public-domain software.